Apparatus for making electrical



Nov. 2 1926.

w. A. BRAUN ET AL APPARATUS FOR MAKING ELECTRICAL HEATING UN ITS Filed June 10, 1925 2 Sheets-Sheet 1 ATTORNEYS.

Nov. 2,1926. 1,605,889

Y W. A. BRAUN ET AL APPARATUS FOR'NAKING ELECTRICAL HEATING UNITS Filed June 10 H 1925 2 Sheets-Sheet 2 'Fija. -9

mmmn' 4/ m as i%\\\*1 ,0 a F i 4. 2 7 H 11 1' 1" 7 ATTORNEYS Patented Nov. 2, 19260 entra n 'srres earner WILLEAIJI A. BBAUN AND CHARLES MAURER, OFJJOVER, OHIO, ASSIGNORS T0 DOVER MANUVFAGTURING CO., OF IJOVER vCPI-I10.

A?PABA.TUS-FO R MAKINQ ELECTRICAL .I-IEATIN'G UNITS.

Application filed June 10, 1925. Serial No. 36,128.

This invention relates to improvements in methods of and apparatus for, making heating units with particular reference "to that class of units in which a resistance wire is embedded in a suitable di-electric material within a shallow container which 'forms a portion of the unit when completed. Oommon examples of such heat units are to'be found in sad irons, vulcanizers, and other articles in which the container is necessarily of highly conductive material and in which the resistance wire is located 'in close proximity to the wall of the container but necessarily electrically insulated therefrom in such a manner as to avoid short circuits. The embedding material must not onlybe highly di-electric but it must also be capable of holding the resistance wire'in plice and it must possess maximum heat conductivity whereby the heat generated by'the electric current in the wireymay be rapidly conveyed and distributed throughout the wall of the container to be heated.

Heretotore the operation of preparing the resistance wire and inserting it in the embedding material has been a diiiicult :operation requiring considerable time, care, and skill on the part of the workmen inor-der to avoid short circuits between successive loops or portions ol the wire and between the wire It is the oband the wall of the container. ect of this invention to provide a more simple and more expeditious method and one which can be practiced by comparatively unskilled employees and in which unitorm results may be attained, the dangero'j short circuits being eliminated and'the resistance wire being unfailingly and uniformly embedded and held in'the embedding material of the in a predetermined spaced relation various portions to eachother and to the wall of the container. Y

A further object of this invention is to provide an improved apparatus to facilitate the practice of said method; to provide a supporting form upon which a helical coil of the required length may be looped'and held for annealing 'purposes in the position which the wire is to occupy in the completed unit and the form then utilized to carry the wire into the embedding. material and support it therein while such material is being hardened or made capable of mechanically retaining the wire after the form has been withdrawn. Also to p'rovidea' holding embedding material.

proved method as seen from the side at which the resistance wire is applied, and shoi'ving-a helicall'y coiled resistance wire in position thereon preparatory to the anneal- 1g thereof or the insertion thereot'into the is used in the manufacture of sad irons.

Figure 2 is a sectional view drawn to line 2-2 of Figure 1.

Figure 3 is a similar view showing the form in the positionw'hichit occupies when holdin the resistance wire coil in an iron base having a recess partially filled with embedding material.

Figure 4 1s a s milar View of the sad iron base; embedding material, and resistancewire as it appears after the form has been withdrawn.

Figuret is a similar view of the parts shown inFigure4 with an additional layer of embedding material in the recess and showing also a'ifragment ofa press plunger for compressing said material.

Figure 6 is a similar view showing the heating unit as it appears after the cover plates have been applied.

Figure? is a sectional view oi the form drawn on line 7-7 of Figure 1.

like parts are identified by the same reterence characters throughout the several views.

In the. practice of the improved method a resistance WllG'Oi the required length and cross section is first wound into a at coil 1 of small diameter. The diameter of the coil ispreterablyabout halt oi? the thickness of the layer of embedding material which is to receive it. This coil. is then looped or turned upon itself into the posi tion'which it is to'o'ccupy when embedded in thecontainer or recessed base, the "form ot' the loops and their position being such as to obtain desired heat distribution. in

the manutacture'ot sad irons it is deiirabtc to so "form the'loops that there Will be a The form illustrated plurality of portions of the coil extending along each side in the direction of the point with the ends brought into proximity in the rear portion and extended upwardly for connection with the conducting wires oi an electric circuit.

The wire is looped in the desired position upon a supporting form which is adapted to be withdrawn without disturbing the loops. lVhile the wire is on this form it is annealed to reduce or eliminate its elastic tension or internal resistance to the bending stresses. The holding form is then used as a carrier to convey the looped coil into a layer of plastic embedding material, pr ably a material which becomes plastic or semi-liquid by the addition of water but which tends to harden when dry and which may be baked in the form of a brick. The holding form is utilized to hold the coil or wire in its embedded position when the wire embedding material is being dried or otherwise hardened suiiiciently to retain the wire. The form is then withdrawn and an additional layer of semi-liquid or plastic embedding material applied to fill voids and to completely cover the, wire. Thereafter the embedding material is again dried, pressed and halted. In the manufacture of sad irons and similar articles a metallic base is em ployed which is suitably recessed to receive the layers of embedding material with the wire therein in spaced relation to the walls of the base or container and the wire is so positioned or looped in this recess as to provide the desired heat distribution over or throughout the bottom surface of the base.

Referring to Figure 1 .it will be observed that the helically coiled wire is arranged in loops having portions 1, 2 and 3 extending along one surface of a di-electric form or plate l on each side of the longitudinal center of the form. In the rear portion of the form one end 01"- the coil is formed into additional loops with short portions 5, 6, 7 and 8 extending back and forth, with the extremity of the coil leading to a tubular stud 9 through which the uncoiled extrem ity of the wire passes. On the other side of the longitudinal center line the other end portion 12 of the coil extends to a tubular stud 15 through which the uncoiled end portion 10 of the wire passes.

The portions 1, 2, 3, 5, 6, 7, 8 and 12 of the wire coil are held in position by positioning pegs which are secured to the plate a and arranged in suitable rows to receive the coiled wire between them. The pegs of the outer row have semi-cylindrical portions 20 and reduced end portions 21. The wire coil is received upon the shoulder 22 at the outer end of the semi-cylindrical portion 20. The flattened sides of the semicylindrical portion 20 are adapted to fit against the side Wall 25 of the base or con tainer 26 shown in Figure 3 when the form is inserted therein for the purpose of pose tioning the wire and holding it in the layer 27 of embedding material. The pegs in the inner rows preferably have cylindrical portions 30 corresponding with the semi-cylindrical portions 20 oi the pegs in the outer row and reduced extremities 31 corresponding with the reduced extremities 21 or the pegs in the outer row. But while the pegs of the outer row may be and preferably are formed of metal so that they will n t break when brought into contact ih the metal wall oi the recessed container the pegs of the inner rows are preferably forme'l or? dielectric material secured to the plate i by metal pins The material oi which the inner pegs is composed is non-frangible and non-combustible under the temperatures to which this material is subjected, a composition of lava or of asbestos and carbon being preferably employed. The plate dis also formed of similar material, the material commercially known as bakelite being preferred, although any other material possessing the necessary rigidity and which has a low coeiiicient of expansion and contraction and which will not warp or break in ordinary use, may be used.

To facilitate manipulating the form and also to provide means whereby it may be rigidly secured to the base or container, I preferably provide the plate a with a centrally disposed swiveled thumb piece 38 having a screw threaded end portion which projects into the space between the inner rows of coil holding pegs and which is adapted to be screwed into a socketed stud 39 formed in the base or container and so positioned as to receive the threaded end of the thumb piece when the outer rows oi pegs or portions 20 thereof are in registry with the side walls of the recess.

The form 4; is provided with a set oifgauge pins 10 having reduced end portions oi greater length than those of the pegs heretofore described. These gauge pins it) are otherwise preferably formed in the same manner as the pegs heretofore described their inner portions being flattened if in the outer row or cylindrical if in the inner row. They preferably constitute a portion of the series of pegs upon which the wire coil is supported. I

The use of the form will be readily understood from the above description but will here be briefly reviewed. After forming the resistance wire into a helical coil, except as to the end portions, one end portion is passed through one of the tubular studs 9 or 15 and the coil is then looped over the pegs as shown in Figure 1 until its other unwounded end can be passed through the companion tubular stud. These unwound ends project from the rear face of the plate 1,

embedding material.

ne'oasse' i. e. the upper face when the form is in the position in which it is shown in Figure 3; 'l hey are connected with electric circuit ter minals and electric currentin sufficient voltune and pressure is passed through the wire to heat it to a cherry red. It is then allowed to cool slowly to approximately normal atmospheric temperature. The lava coating upon all but the outer row of pegs prevents short circuiting while the current is being passed through the wire. Thereupon the form is adjusted to the container or base as shown in Figure 3, thereby carrying the coil of wire into the recess, said recess having been previously partially filled with semiliquid or plastic embedding material. The wire will be embedded therein to a depth which is determined by the gauge pins all), i. e. by the length of the reduced end portions of the gauge pins, the shoulders ll of which are in the same plane with the shoulders 22 and 22 on all of the pegs above dcscribed. lhese gauge pins co-operate with the pins of the outer row having the flat tened side surfaces 20 to secure an accurate positioning of the coil in the container or base.

After the holding form has been utilized to embed the resistance wire as shown in figure 3 it is left in position until the erabedding material has become sufficiently dry and hard tosupport and retain the wire in the position in which it has been placedby the form. 'lhereupon the form is withdrawn, the slightly tapered extremities of the pegs permitting a withdrawal of the form without disturbing the wire. The second layer of embedding material is thereupon applied in a su'lihliently fluid condition to allow it to readily fill the voids left by pegs in the original layer. The second layer is suihciently thick to properly cover the coils. portions of the latter being exposed at the upper surface of the original layer. It will be noted that the original layer is of such thickness and the reduced ends ell of the gauge pins are of such length that the thicker portions of the pegs will not enter the This is desirable to avoid the displacement of the embedding material to an unnecessary extent when the resistance wire is being inserted.

After the second layer of embedding material has been applied it is allowed to dry and harden and then compressed, preferably in a hydraulic press under a pressure of ap proximately forty tons to the square inch, after which the container with the embedding material therein is baked in any suit able manner.

The embedding material used preferably consists of material similar to that described in Letters Patent of the United States No. 1,5302%, dated March 17, 1925 for a composite pack for electrical heating elements.

This material when mined with water may be poured into the containers and when dried may be baked in briclrform by passing an electric current through the wire.

C) The above described pressure 1S applied in order to eliminate voids, force the binding material into the interstices between the grains of fused aluminum oxide to cause said grains to form intimate contacts with the wire and also by shifting the grains, an d pressing them upon each other, to break up the coating films of bonding material which would otherwise tend to envelope the grains. The binding material has less ell-electric strength than the fused aluminum oxide n ins, and also has less heat conductivity. 'lherc'foraby breaking up the liln s of bonding material. which would otherwise envelop the grains,.the di-electric strength and the heat conductivity of the unit is increased.

'lhe pegs-are preferably arranged in rows transverse to the portions of the coil which they support, and in such proximity that they act inpairs to support associated portions of the coilupon the shoulders 22 and between their reduced extremities, each of the intermediate pegs supporting two portions of the coil, one on each side of said reduced extrei'nit-y. The coils are therefore supported in much the same manner that they would be supported ifinounted in channels or grooves in the face of the supporting form but not as continuously, the transverse rows of pegs being located in sufficient prosimity to'keep the coil substantially parallel to the face of the form while allowing a free flow of the material into the coil from all sides and'while causing minimum displ ce ment of embedding material when the projecting portions of the form or reduced er;- treini-ties of the pegs enter such material.

It will, of course, be understood that in Figure 5 the press plate as indicated at as and the head or plate of the press is indicated at 4L6, while in nigure 6 the of the sad iron with the completed heating unit in the recess thereof is assembled with a cover plate 47 and an outer casing or shell 4L8 connected by bolts or screws 49 and 50, respectively in the ordinary manner.

We claim:

1. Apparatus for embedding coils of resistance Wire in semi-liquid embedding material capable of being solidified, comprising a body plate of non-conductive material provided with wire supporting pegs projecting from one surface thereof and having ledges adapted to receive and support a helically coiled wire at points intermediate of the ends of the pegs, and cooperating projections having unledged outer surfaces adapted for contact with the walls of a container whereby the wire may be forced into an embedding material within a receptacle and held out of contact with the walls of such iUU Cia-

receptacle while the embedding material is being solidified.

:2. Apparatus 101 embedding looped coils oi resistance wire in shallow bodies of embedding material, comprising a substantialce thereof series of projections, each hava shoulder and a reduced extremity es:- tendihg beyond the shoule r and said projections being so disposed as to support the coil of wire at various points along its length on the shoulders of two adj acen projections and between the reduced extremities thereof.

3. Apparatus for embedding looped coils of rcs'utance wire in shallow bodies of embedding material, comprising a substantially rigid di-clectric plate having on one surface thereof series of projections, each having a shoulder and a reduced extremity extending beyond the shoulder and said projections being so disposed as to support the coil of wire various points along its length on the shoulders or two adjacent projections and between the reduced ext mities thereof, some of said reduced er iiities being formed to extend beyond LLZJ coil of wire to support it in spaced relation from the .bottom and edges of a container into which said projections and the wire may be inserted.

l. Apparatus for embedding coiled resistance wires in semi-fluid embedding material, comprising a plate, series of wire supporting projections carried by said plate and provided with shoulders upon which said coiled wire may be supported, said plate and portions of said projections being composed of non-combustible di-electric material disposed to prevent short circuiting of an electric current passing through said wire, said projections having tapered extremities be tween which the wire may be supported and y rigid di-electric plate having on one sursome of said extremities being arranged to extend beyond the wire and adapted to act as positioning gauges to space the wire from the bottom and edges of the embedding material.

5. In an apparatus for embedding coils of resistance wire in semi-liquid embedding material capable of being solidified, a holder lOl said wire comprising a body portion of non-conductive materal having wire receiving projections extending from one surface thereof and provided with ledges at intermediate points upon which the wire may be received and held out of contact with the body while being forced into the semi-liqid embedding material, said irojections being located to support the wire between them and having tree extremities suiiiciently distant from the ledges to extend beyond the wire and support it in spaced relation to the bottom of a "ainer, each of said entremities being for; ed for free withdrawal from the wire and from the bottom of the container when the body is lifted.

In an apparatus for embedding coils of resistance wire in a semi-liquid cmbedding material capable of being solidified, a holder for said wire comprising a body portion of non-conducting material provided with series of spaced projections ,between which wire may be looped, each of said projections being provided with intermediate wire receiving let ges and being contoured beyond the ledges for free withdrawal from the wire when the latter is embedded in a material affording resistance to the withdrawal of the wire, some of said projections being also surfaced with non-conducting material adaptec to prevent short circuiting between adjacent strands of wire.

VILLIAM A. BRAUN. CHARLES MAUREL. 

